The objectives of this research are to study the problems of reorganization of axonal and synaptic structures and to relate the potential for plasticity to normal development. I plan to describe the morphological details of developing and mature axons and synapses in two complimentary systems and the anatomical effects on these structures of lesions which produce degeneration or deafferentation. The olfactory cortex and spinal trigeminal nucleus will be studied with light and electron microscopical methods for qualitative and quantitative evaluation of the axonal and synaptic patterns from the onset of synaptogenesis through various stages of maturation and during the sequence of degenerative changes following deafferentation. Two systems will be used so that the observations may have a more general application to the nervous system. Specific attempts will be made to determine the origins and fine structural bases for the initiation and sequence of development for each type of synapse in these two systems and then to compare these with existing, often conflicting, theories of synaptogenesis. Particular attention will be given to observations of differences in axonal and synaptic alterations following deafferentating lesions at specific stages of maturation and the acute and chronic effect of these changes on the resultant neuronal organization in the more mature systems. An important aspect of this study will be the possibility of obtaining new, previously unavailable, information of the anatomical basis for the age-dependent potential of nervous system for plastic adjustment or reorganization.